Derek Hough is excited about returning to “Dancing with the Stars” for his eighth season, but does he reveal who was his favorite partner of all-time? Plus, why is he so fond of his partner this season, Ricki Lake? Also, would he approve of a marriage between his sister, Julianne, and Ryan Seacrest? “Dancing with the Stars” premieres Mon., Sept. 19 at 8/7c on ABC.